It was the turn signal/flasher relay.

I disconnected both side markers completely to return to operating mode w/o the side markers. Neither the f & r turn signal nor the hazards worked. I broke down and bought a new turn signal/flasher combo relay ($US60). I then disconnected the battery (very important), put the relay in, hooked up the side markers, and everything worked like a charm. I'm pretty sure I must have shorted something out when I first installed the side markers since I neglected to disconnect the battery. A mistake that brought the total cost of installing the side markers to over $120, plus countless hours trouble-shooting the problem.

As a post-mortem, I would say the following for anyone wanting to install side marker lights on an s/v 70:
1) The side marker lights are not pre-wired, as many people thought. You need to buy the lights with the harnesses.
2) The lights fit perfectly in the holes in the front fenders where the Ovlov emblem is.
3) It is easy to fish the wires through the fenders. Start in the front and push the fish tape (wire hanger) back to the hole.
4) The connections are very simple and the splice crimps that come with the installation kit work well.
5) Disconnect the battery before doing touching the wiring!!
6) If you need more information other than what is in this thread, I can send you the connection instruction from IPD in pdf.

Many thanks for the support and ideas from n0v8or!